Field of the Invention
The invention is related to a resistive random access memory (RRAM), and particularly related to an RRAM having a transparent conductive oxide layer.
Description of Related Art
In general, an RRAM includes a top electrode (TE), a bottom electrode (BE) and a transition metal oxide (TMO) between the TE and BE, and may be connected to the outside via a top wire and a bottom wire. Since the conductive path in the RRAM is controlled by means of oxygen vacancies under a low resistance state (LRS), the oxygen ions diffusion that is easily affected by temperature difference is the key factor in controlling thermostability of the RRAM. For example, it is often hard to retain a Ti/HfO2 type RRAM currently employed in LRS under high temperature, leading to deterioration in the so-called “high-temperature data retention” (HTDR).
Therefore, there have been a variety of techniques for reducing diffusion of the oxygen ions into the TMO, such as increasing a Set power, which, however, affects the yield for Reset. Moreover, there is a technique of using an extremely thin insulating oxide between the electrodes and the TMO to block the diffusion of the oxygen ions, but it may impact on the conductivity of the memory as a whole and also requires accurate process control.